1. Field of the Invention
The present invention relates to a print dipole antenna and manufacturing method thereof; in particular, the present invention relates to a print dipole antenna providing advantages of multiple resonance frequencies, wide frequency band as well as manufacturing method thereof.
2. Description of Related Art
The print dipole antenna provides quite a few advantages in terms of such as slim size, low cost, simple structure, convenient fabrication processes and suitability for integration with solid state devices or microwave integrated circuit modules, thus the print dipole antenna has widely applied in various wireless communication and radar systems. Since the conventional dipole antenna is the narrow frequency band antenna capable of single resonance frequency, many efforts and researches have been devoted to the extension of frequency bandwidth of the print dipole antenna and the increase of its resonance frequency; for example, a print dipole antenna using a double-sided substrate structure in combination with BALanced to UNbalanced (Balun) transformer, or by means of tapered slot feed, or else some proposed a dipole antenna through double-sided integration and the like, and all these approaches may effectively increase the frequency bandwidth; additionally, by adding parasitic metal components or extending dipole antenna arms, it is allowed to excite different resonance modes, so as to achieve the effect of multiple frequency band resonance.
The excitement current plays a significant role in the radiation effect of the dipole antenna. When the current distribution is changed, the radiation field and the polarity orientation may accordingly vary, so the phase and the amplitude of the current signal may almost dominantly determine the radiation effect of the dipole antenna. In a general dipole antenna, based on the design idea, it is undesirable to generate unbalanced current, because the feedings of current having differences in phase or amplitude at two dipole arms may possibly interfere with the expected antenna radiation effect and polarity orientation, while most of the existing documents or research reports are addressed to the issues of unbalanced current phenomenon, rather than providing the dipole antenna specifically designed for unbalanced current.
The conventional print dipole antenna is characterized in single resonance frequency, but limited frequency bandwidth can no longer satisfy the demands in practical applications; whereas improvements proposed at present are mostly designed in terms of structural modifications, which usually require extra extension in structure thereof to increase frequency bandwidth and resonance frequency, thus leading to enlargement in integral antenna area or volume. This consequence is undesirable for the goal of slimness and compact in size, and therefore becomes a challenging issue for the conventional technologies to overcome. Furthermore, balance signal is needed to be fed at the center of the conventional print dipole antenna, thus limiting the feed structure and degrees of freedom, and also the Balun transformer may occupy extra space on the print circuit board and cause unexpected interference to the print dipole antenna.